1. Field of the Invention
The present invention relates to a functional film preferably used as a sealing substrate of an organic EL device in which a light emitting element is protected with a passivation film.
2. Description of the Related Art
An organic EL device (OLED device) including an organic electro luminescence (EL) material is used in displays, illumination devices, and the like.
The organic EL material used in the organic EL device is extremely vulnerable to moisture. Therefore, for the organic EL device, a structure in which the peripheral portion thereof is sealed with a glass plate or a metal plate is adopted to prevent deterioration of the organic EL material due to moisture.
However, in such a method, because the entirety of the device is sealed with a metal or glass, the organic EL device becomes heavy and thick. Furthermore, with such a method, it is difficult to follow the recent trend that requires organic EL devices, which use the organic EL unit such as an organic EL display, to be more flexible.
In order to solve the above problems, as disclosed in JP2010-198926A and JP5036628B, a method has been developed which is for lightening and thinning down an organic EL device by giving gas barrier properties to a light emitting element (organic EL element) including an organic EL material.
Specifically, by adopting a laminate structure (organic EL laminate) obtained by covering a light emitting element, which has an organic EL material, an electrode, and the like on an element substrate, with a passivation film (protective film) having gas barrier properties and attaching a sealing substrate onto the passivation film by using an adhesive, deterioration of the light emitting element due to moisture is prevented.
According to the aforementioned documents, examples of materials forming the passivation film in such an organic EL laminate include inorganic materials such as silicon nitride, silicon oxide, and silicon oxynitride that exhibit gas barrier properties.
Furthermore, according to the aforementioned documents, examples of materials forming the sealing substrate include glass, plastic, quartz, resins, metals, and the like.
If the constitution including the passivation film and the sealing substrate is adopted, the periphery of the organic EL device does not need to be sealed with a metal plate or a glass plate, and therefore the organic EL device can be lightened and thinned down.
In order to further lighten and thin down the organic EL device in a better way, it is more advantageous to use a plastic film than to use glass or the like as the sealing substrate.
In such an organic EL laminate having the sealing substrate, generally, the sealing substrate adheres to the organic EL device (passivation film) by an adhesive.
Meanwhile, a sealant is also known which is for so-called heat sealing by which the sealant material is melted by heating and attaches members to each other as described in JP2008-1760A and JP2011-526052A. As is well known, the surface of the organic EL device has irregularities resulting from the light emitting element formed thereon. If the sealing substrate is heat-sealed by using the aforementioned sealant, it is possible to seal the organic EL device with the sealing substrate while concealing the irregularities on the surface of the organic EL device with the molten sealant.